Ees 101 Iii--7Th Column

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Volcanoes

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--- is an opening (or rupture) in the Earth's surface or crust, which allows hot, molten rock, ash, and gases to escape from deep below the surface.
--Volcanoes are generally found where two to three tectonic plates pull apart or are coming together.

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Pyroclastic Debris

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Fragmented material that sprayed out of a volcano and landed on the ground or sea floor in solid form.

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Volcanic Ash

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consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions,[1] less than 2 millimetres (0.1 in) in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact with water causing phreatomagmatic eruptions, and ejection of entrained particles during steam eruptions causing phreatic eruptions.[2] The violent nature of volcanic eruptions involving steam results in the magma and solid rock surrounding the vent being torn into particles of clay to sand size.

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Lapille

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Pea- to walnut-size pyroclasts (2 to 64 mm). They often look like cinders.

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Pele's tears or Pele's hair

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is a geological term for small pieces of solidified lava drops formed when airborne particles of molten material fuse into tearlike drops of volcanic glass. Pele’s tears are jet black in color and are often found on one end of a strand of Pele's hair. Pele's tears is primarily a scientific term used by volcanologists.

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Blocks and Bombs

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---volcanic block is a fragment of rock that measures more than 64 mm (2.5 in) in diameter and is erupted in a solid condition.
---A volcanic bomb is a mass of molten rock (tephra) larger than 65 mm (2.5 inches) in diameter, formed when a volcano ejects viscous fragments of lava during an eruption. They cool into solid fragments before they reach the ground.

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Tuff

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tuff, a relatively soft, porous rock that is usually formed by the compaction and cementation of volcanic ash or dust.

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Tephra

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It is solid material ejected by a volcano, and may include ash, rock, and cinders.

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Pyroclastic Flow

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is a fast-moving current of superheated gas (which can reach temperatures of about 1,000 °C (1,830 °F)) and rock (collectively known as tephra), which reaches speeds moving away from a volcano of up to 700 km/h (450 mph).[2] The flows normally hug the ground and travel downhill, or spread laterally under gravity. Their speed depends upon the density of the current, the volcanic output rate, and the gradient of the slope. They are a common and devastating result of certain explosive volcanic eruptions.

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Ignimbrite

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is the deposit of a pyroclastic density current, or pyroclastic flow, a hot suspension of particles and gases that flows rapidly from a volcano, driven by a greater density than the surrounding atmosphere.

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Lahars

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is a type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris, and water. The material flows down from a volcano, typically along a river valley

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Volcaniclastic Deposits

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Where the volcanic material has been transported and reworked through mechanical action, such as by wind or water

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Vesicles

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texture characterised by a rock being pitted with many cavities (known as vesicles) at its surface and inside

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Magma Chamber

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is a large underground pool of molten rock found beneath the surface of the Earth. The molten rock in such a chamber is under great pressure, and given enough time, that pressure can gradually fracture the rock around it creating outlets for the magma. If it finds a way to the surface, then the result will be a volcanic eruption; consequently many volcanoes are situated over magma chambers.

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Fissure

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is a linear volcanic vent through which lava erupts, usually without any explosive activity. The vent is usually a few meters wide and may be many kilometers long. Fissure vents can cause large flood basalts and lava channels.

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Caldera

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is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US.

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Shield Volcano

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a type of volcano usually built almost entirely of fluid lava flows. They are named for their large size and low profile, resembling a warrior's shield. This is caused by the highly fluid lava they erupt, which travels farther than lava erupted from more explosive volcanoes.

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Cinder Cone

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s a steep conical hill of volcanic fragments that accumulate around and downwind from a volcanic vent.[1] The rock fragments, often called cinders or scoria, are glassy and contain numerous gas bubbles "frozen" into place as magma exploded into the air and then cooled quickly.[1] Cinder cones range in size from tens to hundreds of meters tall.[1] Cinder cones are made of pyroclastic material.

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Stratovolcano
or composite volcano

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is a tall, conical volcano built up by many layers (strata) of hardened lava, tephra, pumice, and volcanic ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile and periodic, explosive eruptions.

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Viscosity

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Viscosity is defined as the ability of a substance to resist flow

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Effusive

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is a volcanic eruption characterized by the outpouring of lava onto the ground (as opposed to the violent fragmentation of magma by explosive eruptions). Lava flows generated by effusive eruptions vary in shape, thickness, length, and width depending on the type of lava erupted, discharge, slope of the ground over which the lava travels, and duration of eruption.

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Explosive

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an eruption is driven by gas accumulating under great pressure. Driven by hot rising magma, it interacts with ground water until the pressure increases to the point at which it bursts violently through the overmantle of rock. In many cases, the rising magma will contain large quantities of partially dissolved gas.

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Phreatomagmatic eruption

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are eruptions that arise from interactions between water and magma. They are driven from thermal contraction (as opposed to magmatic eruptions, which are driven by thermal expansion) of magma when it comes in contact with water. This temperature difference between the two causes violent water-lava interactions that make up the eruption. The products of phreatomagmatic eruptions are believed to be more regular in shape and finer grained than the products of magmatic eruptions because of the differences in eruptive mechanisms.[1][33]

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Lava

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Molten rock that reaches the earth's surface through a volcano or fissure.

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A'a'

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Hawaiian word used to describe a lava flow whose surface is broken into rough angular fragments.

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Pahoehoe

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meaning "smooth, unbroken lava") is basaltic lava that has a smooth, billowy, undulating, or ropy surface. These surface features are due to the movement of very fluid lava under a congealing surface crust.

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Columnar Jointing

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Joints can also form via cooling of hot rock masses, particularly lava, forming cooling joints, most commonly expressed as vertical columnar jointing.

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Pillow Lava (Pillow Basalt)

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Pillow lava is the lava structure typically formed when lava emerges from an underwater volcanic vent or subglacial volcano or a lava flow enters the ocean.

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Island Arc

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An island arc is a type of archipelago composed of a chain of volcanoes which alignment is arc-shaped, and which are situated parallel and close to a boundary between two converging tectonic plates.

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Continental Arc

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orm when oceanic crust subducts beneath continental crust on an adjacent plate, creating an arc-shaped mountain belt.

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Rifts

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is a place where the Earth's crust and lithosphere are being pulled apart[1] and is an example of extensional tectonics.[2]

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Mid-ocean Ridge

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a general term for an underwater mountain system that consists of various mountain ranges (chains), typically having a valley known as a rift running along its spine, formed by plate tectonics. This type of oceanic ridge is characteristic of what is known as an oceanic spreading center, which is responsible for seafloor spreading.
***located at divergent boundary

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Large Igneous Provinces

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'LIP' is now frequently used to also describe voluminous areas of, not just mafic, but all types of igneous rocks.